1. Field of the Invention
The present invention relates to land fills and a method of forming a below ground receptacle or land fill for the storage and containment of solid and/or liquid waste materials. Many solid waste materials are capable of leaching out fluids during storage and containment, which fluids present hazards to the environment, especially when the leached out material comes in contact with ground water supplies.
More particularly, the present invention relates to a new and less costly method of containing waste liquids and leachable waste solids, including provision for the permanent storage of waste materials in a preformed pit that is formed as a result of the excavation or mining of a naturally occurring deposit of water-swellable, colloidal clay, such as bentonite-clay.
The storage of waste materials in a land fill cavity or pit that remains after mining and removal of water-swellable colloidal clay from the earth in accordance with the present invention makes use of a naturally compacted layer of clay which is left undisturbed in place and which layer provides an unexpectedly highly efficient, water-impermeable, natural pit liner that is highly economical, and durable for long periods of time. The naturally compacted bentonite layer eliminates the need for installing artificial or man-made bentonite liners and/or eliminating the need for installing plastic sheeting materials in a land fill pit prior to the storage and containment of waste material.
The laws and regulations issued by the EPA, RECRA and other State and Federal regulatory agencies are becoming increasingly more stringent and complex with respect to the lawful use of land fills for storing and containment of waste materials, particularly toxic waste materials, such as polychlorinated biphenyls, dioxins and the like. Burial of waste materials in the earth in the past has resulted in the leaching out of harmful materials, which materials sometimes pass through the soil bed beneath the originally introduced materials and eventually find their way into ground water supplies used for potable water, agriculture, and industry. When this does occur, both the soil and water supplies become contaminated with a resultant, almost immeasurable, human damage and economic cost. Regulations directed at land fills for highly toxic waste materials are now very stringent in order to make sure that the soil bed and water supplies beneath a land fill are permanently protected. These regulations generally do not permit the drainage or leaching out of any of the buried, potentially harmful, waste material in a land fill pit to pass through the soil bed below the land fill because of the possibility that these materials may eventually contaminate neighboring ground water supplies.
2. Description of the Prior Art
The present difficulties in the lawful burial, handling and containment of waste materials, particularly toxic materials, are well recognized and have resulted in alternative, and prohibitively expensive methods of waste material disposition, including recycling, waste-stream treatment, and incineration.
Land fill disposal of aqueous, or potentially aqueous, toxic substances typically requires systematically lining the surface area of a land fill cavity or pit with an artificially formed barrier of water-impermeable material, such as a layer of bentonite, or other water-swellable, colloidal clay, or a layer of bentonite laminated to one or more layers of an impermeable liner, such as polyethylene film so that toxic materials leaching out from the mass of waste material in the pit cannot penetrate through the artificially installed liner and eventually move into a ground water supply.
Bentonite clays have played an integral part in some land fill lining methods, as disclosed in U.S. Pat. Nos. 4,693,923 (McGroarty), 4,255,067 (Wright), 4,656,062 (Harriett), 4,501,788 (Clem), 4,344,722 (Blias), 3,986,365 (Hughes) and British Patent No. 1,029,513.
The McGroarty, Harriet, Wright, and British patents disclose a soil bed liner including a water-impermeable, polymeric material as an integral element thereof useful for waste material containment. The Harriet and McGroarty patents also disclose an additional or second, water-impermeable layer of bentonite clay particles adhered onto an impermeable polymeric liner. British patent No. 1,029,513 discloses the concept of providing a second layer of foamed plastic or resinous material filled with bentonite.
The Wright patent discloses a bentonite layer sandwiched between two sheets of 10-20 mil thickness, flexible, water-impermeable polymeric sheet material.
Blias U.S. Pat. No. 4,344,722 discloses a waterproofing article formed by a layer of bentonite particles sandwiched between two water-permeable membranes.
Clem U.S. Pat. No. 4,501,788 discloses the concept of adhering bentonite particles onto a vapor-permeable, non-biodegradable support.
Published European Patent Application No. 0059625 to Clem discloses a first layer of moisture-permeable, sheet material containing bentonite particles and having a plurality of layers disposed on both sides of the sheet.
The above-described patents generally disclose the concept of incorporating bentonite as an important element of the inventions thereof and, these patents generally teach or suggest that bentonite particles be adhered to both water-permeable or water-impermeable type flexible films or membranes. These membranes are also used to cover exposed, absorbent earth surfaces in a below-grade pit or containment area. The procedure of lining a large pit or excavation with a bentonite-containing waterproof liner is a relatively costly process and is not always completely effective because "breaks" often exist or form in an installed lining over time. Such breaks sometimes occur prior to, during or after the initial placement of the liner or during the deposition of waste materials into a previously lined pit.
Other approaches to the problem of providing water-impervious, flexible liners for land fill sites include the mixing of bentonite with native soil, the compacting of native soil and/or the mixing of clay with soil and a water-retaining polymer. For example, Hughes U.S. Pat. No. 3,986,365 discloses the concept of mixing equal parts of soil and bentonite and adding to this mixture a water-retaining polymer in order to retain water in a land fill.